Quaternary Semiconductor Research Articles

Correlation of Space Charge Limited Current and γ-Ray Response of CdxZn1-xTe1-ySey Room-Temperature Radiation Detectors

In this letter we report a direct correlation between the space charge limited current flow and radiation detection properties of Cd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-y</sub> Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> (CZTS) detector. CZTS is a recently discovered quaternary wide bandgap semiconductor for room-temperature gamma photon detection. The CZTS single crystals have been grown in-house using a modified Bridgman technique. Planar detectors were fabricated and characterized in terms of charge carrier flow and radiation detection measurements. An anomalous current flow falling outside the Lampert's triangle in logJ - logV plot, has been observed which is not generally seen in semiconductor detectors governed by space-charge limited current flow mechanism. The anomalous behavior has been attributed to the presence of electron traps. The devices were tested for their radiation detection properties by acquiring pulse height spectra using <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">241</sup> Am and a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs isotopes as a source of alpha particles and gamma photons, respectively. It was further noticed that the only detectors which worked satisfactorily as radiation detectors, did not exhibit the anomalous current flow mechanism.

Cu2Zn(Si,Ge)Se4 quaternary semiconductors as potential photovoltaic materials

The geometric and electronic structures of Cu2ZnSixGe1-xSe4 alloys are studied using density functional theory calculations. The variation of lattice constants is less than 1.2%. Negative formation enthalpies are obtained, indicating these alloys are completely miscible. The conduction band minimum gradually shifts upward with the Si concentration, resulting in a tunable bandgap from 1.27 to 2.26 eV. The bandgap of the Cu2ZnSi0.25Ge0.75Se4 alloy is very close to the optimal value. Compared with other two well-studied alloys with the optimal bandgap (Cu2ZnSi0.5Sn0.5Se4 and Cu2ZnSnS4), the Cu2ZnSi0.25Ge0.75Se4 has a red-shift in the optical absorption edge, highest absorption coefficient and smallest transmittance.

Cu/Zn disorder in stoichiometric Cu2ZnSn(S1-xSex)4 semiconductors: A complementary neutron and anomalous X-ray diffraction study

The quaternary compound semiconductor Cu2ZnSn(S1-xSex)4 (CZTSSe) which crystallizes in the kesterite-type structure, is a promising material to be used as p-type absorber layer in thin film solar cell applications based on earth abundant elements. The absorber band tailing caused by an exceptionally high Cu/Zn disorder is believed to be one of the reasons for the limited open-circuit voltage in CZTSSe-based photovoltaic devices. This work is an experimental study of the Cu/Zn disorder in a unique set of single phase, stoichiometric CZTSSe mixed crystals, synthesized by solid state reaction, by means of neutron powder diffraction and anomalous X-ray powder diffraction. The existence of Cu/Zn disorder was revealed as the only intrinsic point defect in these mixed crystals within the detection limits of our measurements. The order parameter Q was calculated on the basis of the occurring CuZn and ZnCu anti site defects causing the Cu/Zn disorder. Variations of the order parameter with anion composition and the effect on the optoelectronic properties of the partial substitution of Se with S in Cu2ZnSn(S1-xSex)4 was elaborated.

Polypyrrole-Bonded Quaternary Semiconductor LiCuMo2O11-Graphene Nanocomposite for a Narrow Band Gap Energy Effect and Its Gas-Sensing Performance.

In this study, we demonstrate the fabrication and characterization of a new quaternary semiconductor nanocomposite of LiCuMo2O11/graphene oxide/polypyrrole (LCMGP) via a hydrothermal method and testing of an NH3 and H2SO4 sensor operating in gaseous states at room temperature. We used X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to characterize the properties of LCMGP nanostructures. Our sensor is capable of detecting NH3 and H2SO4 and quantifying their concentration in the gas flow. These results have been confirmed by exposing the sensor to different concentrations of NH3 and H2SO4 (100–1000 ppm). The obtained results confirm the exceptional sensing properties of the graphene–polymer-combined quaternary semiconductor nanocomposite related to the oxidation–reduction process that can be used for detection, identification, and quantification purposes.

Partial and Total Substitution of Zn by Mg in the Cu2ZnSnS4 Structure

Cu 2 ZnSnS 4 (CZTS) is a quaternary semiconductor that has emerged as a promising component in solar absorber materials due to its excellent optical properties such as band-gap energy of ca. 1.5 eV and significant absorption coefficient in the order of 10 4 cm − 1 . Nevertheless, the energy conversion efficiency of CZTS-based devices has not reached the theoretical limits yet, possibly due to the existence of antisite defects (such as Cu Zn or Zn Cu ) and secondary phases. Based on electronic similarities with Zn, Mg has been proposed for Zn substitution in the CZTS structure in the design of alternative semiconductors for thin-film solar cell applications. This work aims to study the properties of the CZTS having Mg incorporated in the structure replacing Zn, with the following stoichiometry: x = 0, 0.25, 0.5, 0.75, and 1 in the formula Cu 2 Zn 1 − x Mg x SnS 4 (CZ-MTS). The semiconductor was prepared by the hot injection method, using oleylamine (OLA) as both surfactant and solvent. The presence and concentration of incorporated Mg allowed the fine-tuning of the CZ-MTS semiconductor’s structural and optical properties. Furthermore, it was observed that the inclusion of Mg in the CZTS structure leads to a better embodiment ratio of the Zn during the synthesis, thus reducing the excess of starting precursors. In summary, CZ-MTS is a promising candidate to fabricate high efficient and cost-effective thin-film solar cells made of earth-abundant elements.

Application of Schrödinger equation in quantum well of Cu2ZnSnS4 quaternary semiconductor alloy

An approximate solution of the radial Schrödinger equation is obtained with a generalized group of potentials in the presence of both magnetic field and potential effect using supersymmetric quantum mechanics and shape invariance methodology. The energy bandgap of the generalized group of potentials was calculated for s−wave cases at the ground state. By varying the numerical values of the potential strengths, the energy band gap of Hellmann's potential and Coulomb-Hulthẻn potential respectively were obtained. It is noted that the inclusion of the potential effect greatly affects the accuracy of the results. Our calculated results are in agreement and better than the existing calculated results. The present results approximately coincide with the standard bandgap of Cu2ZnSnS4 (CZTS).

Novel designed quaternary CuZnSnSe semiconductor combined graphene-polymer (CuZnSnSe-G-PPy) composites for highly selective gas-sensing properties

We successfully synthesized quaternary nanocomposites containing CuZnSnSe semiconductors combined with graphene-based polymers for selective gas sensing and analyzed their cross-sensitivity using cyclic voltammetry. To investigate the selectivity of graphene-polymer-based detection of different gases was performed for Ammonia (NH3), oxygen (O2), carbon dioxide (CO2), into an emptied vacuum chamber. The sensors provide a direct accurate transformation into electrical signals in devices by recognizing CO2, O2, and NH3. It shows that the sensor has a high selectivity to CO2 by distinguishing with O2, NH3 in vapor-phase intelligently with accurate transformation into electrical signals in devices. Finally, the CuZnSnSe-G-PPy sensors demonstrate fast response/recovery times and a wide range of CO2, O2, NH3 detection. The superior sensing ability of mesoporous CuZnSnSe-G-PPy compared to CuZnSnSe-G and CuZnSnSe eventually is due to the implied optimum amount of synthesized sample. Finally, we proved a facile, low-cost route for the assembly of multiple gas-sensing devices with the potential for vast application.

Resonant tunneling of electrons in AlSb/GaInAsSb double barrier quantum wells

We have studied the optical and electronic transport properties of n-type AlSb/GaInAsSb double barrier quantum well resonant tunneling diodes (RTDs). The RTDs were grown by molecular beam epitaxy on GaSb substrates. Collector, quantum well, and emitter regions are comprised of the lattice-matched quaternary semiconductor Ga0.64In0.36As0.33Sb0.67. Photoluminescence emission spectra reveal a direct bandgap semiconductor with a bandgap energy of Eg≈0.37 eV, which corresponds to a cut-off wavelength of λ≈3.3 μm. The composition-dependent bandgap energy is found to follow Shim’s model. At room temperature, we observe resonance current densities of jres=0.143 kA cm−2 with peak-to-valley current ratios of up to PVCR=6.2. At cryogenic temperatures T&amp;lt;50 K, the peak-to-valley current ratio increases up to PVCR=16.

Pulse-shape analysis in Cd0.9Zn0.1Te0.98Se0.02 room-temperature radiation detectors

The effect of trapping of charge carriers on the shape of the charge pulses from room temperature nuclear detectors, based on a recently discovered quaternary semiconductor Cd0.9Zn0.1Te0.98Se0.02 (CZTS), has been studied. We present a charge-trapping model that explains the pulse shapes for its entire duration from radiation detectors containing multiple defect types. A piecewise continuous model, based on the movement of a large number of charge carriers rather than a single charge, has been proposed to explain the pulse shapes from planar room temperature nuclear detectors. An experimental method based on the model has been described to extract charge-trapping information. This model can be applied to similar semiconductor detectors with electrically active trap centers, in general, to extract information like pre-trapping drift times. Charge pulses from a CZTS planar detector, exposed to 5486 keV alpha particles emitted by a 241Am source, were acquired using a digitizer, and the pulse shapes were explained based on the proposed model. The pre-trapping drift times for electrons as well as holes in CZTS were calculated and studied as a function of operating bias voltage, and a contrast between their bias dependent behaviors was noticed, indicating the behavioral difference of electron and hole traps.

Can Cu2ZnSnS4 nanoparticles be used as heterogeneous catalysts for sulfadiazine degradation?

As a quaternary copper-based semiconductor, Cu2ZnSnS4 (CZTS) is drawing growing attention and is anticipated as a promising photocatalyst, thanks to its large absorption coefficient, exceptional photostability, and theoretical power conversion efficiency. However, CZTS has never been used as an activator of H2O2 for the degradation of refractory organic pollutants. In this study, the synthesis of CZTS nanoparticles obtained with diverse morphologies and crystallinities using solvents of deionized water (CZTS-W) and ethylene glycol (CZTS-EG) was examined in the activation of H2O2 to degrade sulfadiazine (SDZ). The results revealed that CZTS coupled with H2O2 could be an effective system for the degradation of SDZ. Compared to CZTS-EG, CZTS-W presented higher reusability in consecutive cycles with negligible leaching of copper. Reactive oxygen species quenching tests and electron paramagnetic resonance analyses illustrated that •O2−, •OH, and 1O2 contributed to the degradation of SDZ, and 1O2 prevailed over •O2− and •OH. The mechanistic investigation showed that efficient degradation could be associated to the effective recycling of Cu(II)/Cu(I) and low-valent/high-valent sulfur. Also, the degradation pathways of SDZ have been proposed through the detection of intermediate products. This study manifests that CZTS synthesized using deionized water is encouraging for the elimination of organic pollutants.

Structural and optoelectronic characterization of Cu2CoSnS4 quaternary functional photodetectors

Al/p-Si/Cu2CoSnS4/Al quaternary functional semiconductor photodetectors showing solar detector properties were produced via sol-gel method. SEM, EDS and XRD techniques were used in the confirmation of the chemical composition of the photodiodes where nanoparticle like characteristics of Cu2CoSnS4 was seen. UV–vis spectroscopy was used in the investigation of optoelectronic characteristics. It was seen that photodiodes have a high absorption rate with minimum reflectance, bandgap energy was calculated as 1.19 eV. Current – time and current – voltage characteristics of the photodiodes revealed that photodiodes are sensitive to daylight; photodiodes present rectifying characteristics. Thermionic emission theory was used in the calculation of barrier height, ideality factor, photoresponse, photosensitivity, and linear dynamic rate characteristics. Capacitance – voltage, conductance – voltage, corrective capacitance – voltage, corrective conductance – voltage graphs were used to investigate the electrical properties of the Al/p-Si/Cu2CoSnS4/Al photodiodes. The electrical characteristics of the photodiodes reflect frequency dependent characteristics. Such a behaviour was found to be an indication of the existence of interface states. The density of interface (Dit) calculations revealed that the density of interface states strongly depends on AC signal frequency where diminished Dit was seen for increased signal frequency.

Enhanced stability and performance of poly(4-vinylpyridine) modified perovskite solar cell with quaternary semiconductor Cu2MSnS4 (M= Co2+, Ni2+, Zn2+) as hole transport materials

In this work, highly stable and efficient perovskite solar cells (PSCs) in n-i-p configuration has been fabricated. Application of poly (4-vinylpyridine) (PVP) interlayer into the perovskite films via solution based process and quaternary semiconductor Cu2MSnS4 (M = Co2+, Ni2+, Zn2+) (CMTS) nanostructure particles as an inorganic hole transporting material (HTM), result in modified perovskite surface and improving the long term stability and the photovoltaic parameters of the PSCs. The power conversion efficiency (PCE) of the record device with Cu2ZnSnS4(CZTS) HTM and PVP interlayer reaches 13.57%, Voc gains 1.03 V, fill factor (FF) increases up to 70.64% and the device demonstrates low hysteresis (4.14%). Photoluminescence (PL), absorption spectra, electrochemical impedance spectroscopy (EIS) and FESEM images reveal that, the interface between PVP and inorganic CMTS nanostructure particles favorably can reduce non-radiative recombination and enhance Voc. In addition, the presence of hydrophobic PVP interlayer and CMTS nanostructure particles capping with PVP ligands prevent the ingress of the moisture in to the perovskite layer and result in improved stability, where the devices based on CZTS HTM, retain 97% of the initial efficiency after 30 days at room temperature and 35–40% relative humidity.

Solution Deposition of a Bournonite CuPbSbS3 Semiconductor Thin Film from the Dissolution of Bulk Materials with a Thiol-Amine Solvent Mixture.

There is considerable interest in the exploration of new solar absorbers that are environmentally stable, absorb through the visible, and possess a polar crystal structure. Bournonite CuPbSbS3 is a naturally occurring sulfosalt mineral that crystallizes in the noncentrosymmetric Pmn21 space group and possesses an optimal band gap for single junction solar cells; however, the synthetic literature on this quaternary semiconductor is sparse and it has yet to be deposited and studied as a thin film. Here we describe the ability of a binary thiol-amine solvent mixture to dissolve the bulk bournonite mineral as well as inexpensive bulk CuO, PbO, and Sb2S3 precursors at room temperature and ambient pressure to generate an ink. The synthetic compound ink derived from the dissolution of the bulk binary precursors in the right stoichiometric ratios yields phase-pure thin films of CuPbSbS3 upon solution deposition and annealing. The resulting semiconductor thin films possess a direct optical band gap of 1.24 eV, an absorption coefficient ∼105 cm-1 through the visible, mobilities of 0.01-2.4 cm2 (V·s)-1, and carrier concentrations of 1018 - 1020 cm-3. These favorable optoelectronic properties suggest CuPbSbS3 thin films are excellent candidates for solar absorbers.

Theoretical Investigations of Quaternary Semiconductors CsInCdTe3 (Ln = La, Pr, Nd and Sm)

Structural, electronic, optical and thermoelectric properties of quaternary semiconductor materials CsLnCdTe3 (Ln = La, Pr, Nd and Sm) are investigated using density functional theory. Structural parameters such as lattice constants, bulk modulii and bond lengths are found to be consistent with experimental data. The calculated electronic energy band gaps of CsLaCdTe3, CsPrCdTe3, CsNdCdTe3 and CsSmCdTe3 are 1.55 eV, 1.12 eV, 1.23 eV and 1.08 eV. Band gap energies of these compounds exhibit an obvious redshift compared to the base material CdTe (1.59 eV). The optical parameters reveal that these compounds are good dielectric materials. The Seebeck effect, electrical and thermal conductivities and power factor reveal that these compounds are p-type semiconductors.

Cu2FeSnS4 nanoparticles: potential photovoltaic absorption materials for solar cell application

Quaternary semiconductor Cu2FeSnS4 (CFTS) nanoparticle powder have been prepared by a simple chemical technique. The synthesized CFTS nanoparticles have been characterized via powder XRD analysis, Raman spectra, FE-SEM-EDS, UV-Visible absorption spectroscopy, thermal analysis and electrochemical characterization. Powder XRD and Raman spectroscopy confirm the phase and structure of the prepared nanoparticles. The optical absorption studies reveal that the CFTS nanoparticles have a direct optimal band gap in the range from 1.32 to 1.5 eV, which indicates that these nanoparticles are potential absorber materials for thin-film photovoltaic application. The synthesized CFTS nanoparticles were transformed to the ink form and the obtained nanoparticle ink coated on a FTO conducting substrate (surface resistivity-13 Ω sq−1). The catalytic activity of the substrate was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammogram (CV) curves. The appropriate optical band gap and stable electrical properties indicate that Cu2FeSnS4 Nanoparticles are potential materials for thin-film photovoltaic application.

Composition- and Size-Controlled I–V–VI Semiconductor Nanocrystals

Nonisovalent ternary and quaternary semiconductors (i.e., having two or more cations with different valence electrons) have unique structural and electronic properties that are leveraged in photovo...

Comparative studies on hierarchical flower like Cu2XSnS4[X= Zn, Ni, Mn & Co] quaternary semiconductor for electrocatalytic and photocatalytic applications

CXTS [X = Zn, Co, Mn &Ni] has gained increasing interest owing to its application in photovoltaic devices, photocatalysis and electrocatalysis due to its favorable electrical and optical properties. In this work, CXTS has been prepared by hydro-thermal technique and explored as an electrocatalyst and photocatalyst for hydrogen evolution reaction and dye-degradation. From the XRD analysis, we observe that the prepared compound shows tetragonal structure. SEM images reveal that CXTS exhibits flower like architecture. The optical bandgap has been determined to be 1.53, 1.44, 1.42 and 1.37eV for CZTS, CCTS, CMTS and CNTS respectively. For, electrocatalytic activity, it is found that CNTS is preferred for hydrogen evolution with lower Tafel slope value of 76mV/dec and higher current density among the other materials in CXTS. As a photocatalyst CZTS resulted in better degradation of MB dye for about 60% under visible light. The effect of the position of energy bands, surface activity in hydrogen evolution reaction and the impact of recombination of charge carriers on the photocatalytic degradation has been discussed.

Structural Tolerance Factor Approach to Defect-Resistant I2-II-IV-X4 Semiconductor Design

Recent work on quaternary semiconductors Cu2BaSn(S,Se)4 and Ag2BaSnSe4 for photovoltaic and thermoelectric applications, respectively, has shown the promise of exploring the broader family of defec...

Defect Control for 12.5% Efficiency Cu &lt;sub&gt;2&lt;/sub&gt;ZnSnSe &lt;sub&gt;4&lt;/sub&gt; Kesterite Thin-Film Solar Cells by Engineering of Local Chemical Environment

Kesterite-based Cu2ZnSn(S,Se)4 quaternary semiconductor solid solutions are emerging as promising materials for low-cost, relatively benign, high-efficiency thin-film photovoltaics. However, the current state-of-the-art Cu2ZnSn(S,Se)4 devices suffer from cation-disordering defects and defect clusters, which generally result in severe band-tailing, considerable interface and bulk recombination, and ultimately unsatisfactory performance. Herein, we report critical growth conditions for obtaining high-quality Cu2ZnSnSe4 absorber layers with the formation of detrimental intrinsic defects largely suppressed. By controlling the oxidation degree of metal elements and modifying the local chemical composition, we essentially modify the local chemical environment during kesterite thin-film growth, thereby effectively suppressing detrimental intrinsic defects. This modification also activates desirable shallow acceptor Cu vacancies, resulting in increased hole mobility and thereby bulk conductivity of Cu2ZnSnSe4 by two orders of magnitude. As a result, we demonstrate 12.5% efficiency devices with greatly reduced band-tailing and enhanced carrier lifetime. These encouraging results demonstrate not only an essential route to overcome the long-standing challenge of defect control in kesterite semiconductors, but also more generally provide an exemplary strategy to improve the electronic quality for a wider range of multinary compound semiconductors.

Investigations on post sulphurised Cu2ZnSnS4 absorber layer thin films prepared using radio frequency magnetron sputtering

Copper zinc tin sulfide (CZTS) quaternary semiconductor thin films were prepared using binary sulfur rich sputtering targets - copper sulfide (CuS), zinc sulfide (ZnS), and tin sulfide (SnS) by Radio Frequency Magnetron Sputtering with the stacking sequence CuS/ ZnS/ SnS at a substrate temperature of 300 °C. The films were then subsequently sulphurised at 350 °C in Hydrogen Sulfide atmosphere for 60 min. X-ray diffraction studies carried out on the CZTS films revealed the presence of CZTS kesterite phase along the 〈112〉 and 〈220〉 directions. X- ray diffraction results were validated by Raman spectroscopy. The composition of CZTS thin films were confirmed using X-Ray photoelectron spectroscopy and the atomic percentage of the individual elements were quantitatively estimated. The Valance band spectra and Ultra-violet photoelectron spectroscopy were used to study the electronic properties of the sulphurised CZTS thin films. The optical properties of CZTS thin films were studied using Ultraviolet - visible spectrophotometer and the optical band gap was found to be 1.477 eV. The Hall Effect measurements confirmed the p-type nature of the films and the results are discussed.